At the production site of industrial products, the manufacture of defectives is prevented by inspecting whether a target component is non-defective. The inspection of a target component is executed not only in the final manufacturing process of a product but also during the manufacture.
Some inspection processes require high inspection accuracies, but some do not. Inspections vary from one using an inspection apparatus to one based on human subjective evaluation. Compared to a mechanical inspection, an inspection based on human subjective evaluation readily generates an individual difference in inspection. A typical subjective evaluation is a visual inspection by human visual observation. In visual inspection of industrial products, various kinds of features are detected, including the shape and density of a defect. For example, the shapes and sizes of defects such as color inconsistency, stain, and scratch generally handled in visual inspection are not defined, and it is hard to detect such defects. To efficiently perform a visual inspection, demand has arisen for a visual inspection automated by a visual inspection apparatus.
Patent reference 1 discloses a technique of rotating an object to be sensed, changing illumination conditions, and sensing many images. However, it is difficult to detect conditions suitable for a visual inspection from various image sensing conditions. This requests a complicated operation of a user.    Patent Reference 1: Japanese Patent Registration No. 03601031